Atmospheric Pressure Ionization (“API”) ion sources are commonly used to ionize the liquid flow from HPLC or UPLC chromatography devices prior to analyzing the resulting gas phase ions via a mass spectrometer. Two techniques which are most commonly used comprise Electrospray Ionization (“ESI”) and Atmospheric Pressure Chemical Ionization (“APCI”). In ESI techniques, a nebulizer, in the presence of an electric field, converts a liquid sample stream into a spray of charged droplets. As these droplets evaporate, they generate analyte ions.
It is also known to ionize analyte by an Impact spray technique. According to this technique, a nebulizer converts a liquid sample stream into a spray of droplets. These droplets are then directed to impact onto a surface maintained at an elevated electrical potential, thus creating a plurality of ions from the droplets. Typically, this surface may be a stainless steel cylindrical pin. WO 2012/143737 discloses an example of such an Impact spray technique. While the exact mechanisms of ionization in Impact spray techniques are not yet fully understood, it is believed that an essential feature is that droplets impact and bounce off the charged surface. In doing so, these droplets become charged. Subsequently, ions are generated as these droplets evaporate.
It is desired to provide an improved ion source, mass and/or ion mobility spectrometer, method of ionizing a sample, and method of mass and/or ion mobility spectrometry.